This invention relates to a crystalline complex compound of a propargyl alcohol and a tertiary diamine and a process for separating and purifying the propargyl alcohol into a chemically or optically pure form by use of the complex compound.
A propargyl alcohol represented by the Formula (I): ##STR3## wherein each of R.sub.1 and R.sub.2 represents a substituent which is differnt from each other is an important compound as a starting material of an optically active hexa-2,4-diyne-1,6-diol. The optically active hexa-2,4-diyne-1,6-diol is an optical resoluting agent for a wide variety of compounds utilizing a specific inclusion (clathrate) phenomenon. Particularly, its utilization is expected for an optical resolution of raw materials of medicines and agricultural drugs (J. Amer. Chem. Soc., 105, P. 5151, 1983; Tetrahedron Letters, 22, P. 4669, 1981; Chemistry Letters, P. 885, 1985; and Japanese Unexamined Patent Publication No. 169434/1985).
As those which form a crystalline complex compound with the above-mentioned propargyl alcohol, there have conventionally been known brucine and sparteine which are natural substances. By use of a crystalline complex compound of said propargyl alcohol and these natural substances, an optical resolution of the optically active propargyl alcohol has been carried out (see U.S. Pat. No. 4,467,102/1984; Japanese Unexamined Patent Publication No. 55840/1984; Toda, Topics in Current Chemistry, vol. 140, p 44, 1987).
However, in view of the economical point, it is impossible to use such an expensive natural substance as brucine and sparteine to carry out, in an industrial scale, the chemical purification of the compound represented by Formula (I). Accordingly, a purification process which may be readily conducted at lower cost and in an industrial scale is required.
The optical resolution of the compound represented by Formula (I) has been carried out using the natural substances as mentioned above. However, according to such a method, even if any one of the above natural substances is used, it is only one of enantiomers that can be obtained in a high purity, and a complex compound using another enantiomer and a natural substance is obtained in an optical purity of as low as 60 to 80%, since it is poor in crystallizability and is difficult to be purified. Using a compound represented by Formula (I) which is of low optical purity, a hexa-2,4-diyne-1,6-diol is produced to give an optically inactive meso-type substance in addition to the desired optically active hexa-2,4-diyne-1,6-diol. According to the conventional methods, it is not easy to remove this meso substance and thus recrystallization process is required for several times. Therefore, it has been substantially extremely difficult to produce enantiomers of hexa-2,4-diyne-1,6-diols, both of which are of high purity.
Further, the propargyl alcohol represented by Formula (I) is a compound which is usually in a liquid form around room temperature or has its melting point close to room temperature. Therefore, purification by crystallization is not practical due to large loss of the compound. Purification by distillation cannot be adopted since said propargyl alcohols are not thermostable. For these reasons, as a chemical purification method for said compound, a laboratorial method such as column chromatography etc. is usually adopted.